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.Dd July 8, 2018
.Dt Q_QADDQ 3
.Os
.Sh NAME
.Nm Q_QADDQ ,
.Nm Q_QDIVQ ,
.Nm Q_QMULQ ,
.Nm Q_QSUBQ ,
.Nm Q_NORMPREC ,
.Nm Q_QMAXQ ,
.Nm Q_QMINQ ,
.Nm Q_QCLONEQ ,
.Nm Q_CPYVALQ
.Nd fixed-point math functions which operate on two Q numbers
.Sh SYNOPSIS
.In sys/qmath.h
.Ft int
.Fn Q_QADDQ "QTYPE *a" "QTYPE b"
.Ft int
.Fn Q_QDIVQ "QTYPE *a" "QTYPE b"
.Ft int
.Fn Q_QMULQ "QTYPE *a" "QTYPE b"
.Ft int
.Fn Q_QSUBQ "QTYPE *a" "QTYPE b"
.Ft int
.Fn Q_NORMPREC "QTYPE *a" "QTYPE *b"
.Ft QTYPE
.Fn Q_QMAXQ "QTYPE a" "QTYPE b"
.Ft QTYPE
.Fn Q_QMINQ "QTYPE a" "QTYPE b"
.Ft int
.Fn Q_QCLONEQ "QTYPE *l" "QTYPE r"
.Ft int
.Fn Q_QCPYVALQ "QTYPE *l" "QTYPE r"
.Sh DESCRIPTION
The
.Fn Q_QADDQ ,
.Fn Q_QDIVQ ,
.Fn Q_QMULQ ,
and
.Fn Q_QSUBQ
functions add, divide, multiply or subtract
.Fa b
to/by/from
.Fa a
respectively, storing the result in
.Fa a .
Both arguments must be initialized with the same fractional radix point.
.Pp
The
.Fn Q_NORMPREC
function attempts to normalise the precision of
.Fa a
and
.Fa b
if they differ.
The greater of the two precisions is preferred if possible, unless that would
truncate integer component data for the other operand, in which case the highest
precision that preserves the integer component of both
.Fa a
and
.Fa b
is selected.
.Pp
The
.Fn Q_QMAXQ
and
.Fn Q_QMINQ
functions return the larger or smaller of
.Fa a
and
.Fa b
respectively.
.Pp
The
.Fn Q_QCLONEQ
and
.Fn Q_QCPYVALQ
functions attempt to store identical or representational copies of
.Fa r ,
in
.Fa l
respectively.
An identical Q number produced by cloning copies the control bits as well as the
verbatim integer/fractional bits.
A representational copy only copies the values of
.Fa r Ap s
integer and fractional bits, representing them in the bits available per
.Fa l Ap s
Q format.
.Pp
All of those functions operate on the following data types:
.Vt s8q_t ,
.Vt u8q_t ,
.Vt s16q_t ,
.Vt u16q_t ,
.Vt s32q_t ,
.Vt u32q_t ,
.Vt s64q_t ,
and
.Vt u64q_t ,
which are referred to generically as
.Fa QTYPE .
.Pp
For more details, see
.Xr qmath 3 .
.Sh RETURN VALUES
The
.Fn Q_QADDQ ,
.Fn Q_QDIVQ ,
.Fn Q_QMULQ ,
.Fn Q_QSUBQ
.Fn Q_NORMPREC ,
.Fn Q_QCLONEQ
and
.Fn Q_QCPYVALQ
functions return 0 on success, or an errno on failure.
.Er EINVAL
is returned for divide-by-zero.
.Er EOVERFLOW
and
.Er ERANGE
are returned for overflow and underflow respectively.
.Er ERANGE is also returned when the precision of arguments
does not match.
.Pp
The
.Fn Q_QMAXQ
and
.Fn Q_QMINQ
functions return the numerically larger or smaller of their two inputs
respectively.
.Sh SEE ALSO
.Xr errno 2 ,
.Xr qmath 3 ,
.Xr stdint 7
.Sh HISTORY
The
.Xr qmath 3
functions first appeared in
.Fx 13.0 .
.Sh AUTHORS
.An -nosplit
The
.Xr qmath 3
functions and this manual page were written by
.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org
and sponsored by Netflix, Inc.
